A bioassay system, utilizing the hairless mouse, will screen topical agents for effectiveness against epidermal proliferation. Tachyphylaxis of glucocorticosteroids will be investigated with a goal of improved regimens for topical use. Cyclic AMP active agents will be assayed for in vivo activity in epidermal proliferation in hairless mice and psoriasis plaques. Prevention of induction of delayed hypersensitivity by topical glucocorticosteroids will be investigated as well as the possible role of lymphokines in epidermal responses.